The present invention relates to occupant safety systems and more particularly to an energy absorbing or dissipating seat belt retractor using a torsion bar.
Seat belt retractors using torsion bars to absorb or dissipate energy during an accident have been proposed in U.S. Pat. No. 3,970,265. U.S. Pat. No. 4,322,046 shows an alternate torsion bar retractor having a stop mechanism. This stop mechanism unnecessarily extends the size of one side of the retractor.
The present invention provides a novel way of limiting the rotation of the torsion bar without enlarging the exterior dimensions of the retractor. It is an object of the present invention to provide a simple and reliable stop mechanism for a torsion bar of a seat belt retractor. A further object of the present invention is to provide a stop mechanism that is located internal to the retractor spool.
Accordingly the invention comprises: a seat belt retractor comprising: a frame; a hollow spool, for carrying a length of a seat belt, the spool rotationally supported upon the frame; a torsion bar which when stressed can twist or rotate having a first end secured to a first end of the spool and a second end; locking means secured to the second end of the torsion bar for preventing the second end of the torsion bar from rotating during an emergency; and stop means located interior to the spool for limiting the twisting of the torsion bar to a predetermined number of revolutions.
Many other objects and purposes of the invention will be clear from the following detailed description of the drawings.